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Sounds like a lot of RTAA experience out there (good units) so I may as well jump into the mix. I beleive you just weighed in a new Ref charge? What about the oil charge? There is a method (in the IOM as I recall) of checking the oil level. It may be worth a shot. As mentioned, do not try to compare the RTAA and RTAC service wise as they are different designs and and do many things differently. Other things to look at are long periods of low load operation, low temperature operation, use of glycol ( as mentioned). Are you having load/unload problems or just low oil problems?

There is no 3/8 line inside the oil separator so I somehow doubt it could be broken . IOM3 page 83 shows a cutaway drawing of the separator and how it works . The discharge gas enters the separator at the top of the u tube but the entry points are offset to the tube so the gas swirls around causing the oil to separate .

i do not know about any 3/8 line. the above setpoints may point to an issue. i have a feeling that the "saturated evap temp" and compressor suction temp" sensors may be inaccurate but i wanted to know how the above items were set.

Hey guys. I think I have my oil nuisance problem fixed. The unloader valve had a dirty pill filter. I took it out and discarded it. Last time I checked when it started it was around 46%. It never tripped on oil flow after I did that. Now my low suction happens after the unit loads up. The system is very low on glycol. The technician that tested it said it was only 27 degrees. Past the EXV it frosts into the evap but, It is not frosted going to comp. I believe I have an RTAC next to this one and the digital display is showing a 44 suction it shows running normal. Could low glycol cause a low suction since the heat transfer is not as great with just water? Oh by the way we run our chilled water systems at 0 to minus 11. also unit shows 74 then 77 and after the unit runs then it goes back to 74 until unit goes into 7e then shuts down.

At setpoint of 0 to -11 C = 32 to 12.2 F, Your short on freeze protection/glycol. While there may be burst protection with flow, Solution would turn to slush which would cause pump efficiency/flow to drop and cause problems within the evaporator.

heat transfer

Originally Posted by badtech

Hey guys. I think I have my oil nuisance problem fixed. The unloader valve had a dirty pill filter. I took it out and discarded it. Last time I checked when it started it was around 46%. It never tripped on oil flow after I did that. Now my low suction happens after the unit loads up. The system is very low on glycol. The technician that tested it said it was only 27 degrees. Past the EXV it frosts into the evap but, It is not frosted going to comp. I believe I have an RTAC next to this one and the digital display is showing a 44 suction it shows running normal. Could low glycol cause a low suction since the heat transfer is not as great with just water? Oh by the way we run our chilled water systems at 0 to minus 11. also unit shows 74 then 77 and after the unit runs then it goes back to 74 until unit goes into 7e then shuts down.

i believe heat transfer is better or more thermal conductivity with water
than with glycol, you lose btus with glycol

I WILL SELL WORK,GENERATE BUSINESS, GO GET NEW CUSTOMERS!
YOU SHUT THE HELL UP AND QUIT RUNNING YOUR MOUTH!

The best heat transfer is acheived using water alone. When you add glycol the heat transfer starts to get worse and the unit has to work harder to pull out the same amount of heat. Thus the reduction in capacity. The more glycol, the less capacity. There are capacity correction charts for that machine (and others) when using glycol.
There are no parts,tubes, or anything inside the oil seperator. Just a big, ugly, round "U" tube for oil seperation by centrifugal force (as mentioned earlier).

Ok well done on finding the dirty pill filter . did you check the amperage at start up ??
At this point I really think you need to get hold of not only the service bulletins I gave you numbers for but also the main IOM IOM 3 it is a very informative manual and explains how to access all five menus and all the settings for each men . It also shows diagrams and cut away drawings for compressors and oil circuit etc.
One setting to check is in menu 4 for LWT below 38degrees you have to enable the EXV low solution temp gain compensation to properly control the EXV at low LWT"S. This may be your issue ??
All the info is available from your local Trane Office (or possibly Jayguy if you ask nicely) Im not computer savvy enough to know how to send them to you .
also check the chart in the IOM that explains what the ideal settings are for the menu 4 items that Jayguy mentioned ,they are critical and so is the recommended glycol concentration .
good luck Graham